1. Field of the Invention
This invention relates to a lens barrel which is attachable to or detachable from a single-lens reflex camera, for example. More particularly, the invention relates to a lens barrel suitably applicable when a printed-circuit board having various electrical components assembled thereon is incorporated in the portion formed by a fixed cylinder and a rotational cylindrical member comprising a rotary cylinder and others rotatively fitted onto the external side of the fixed cylinder.
Also, the invention relates to a lens barrel which is provided with an image-blur preventive mechanism comprising an optical system for preventing images from being blurred by a camera-shake or the like, and an image-blur preventive driving mechanism to drive this optical system.
Further, the invention relates to an apparatus for incorporating a blur detection sensor which is suitably applicable to a lens barrel provided with an image-blur preventive mechanism comprising an optical system for preventing images from being blurred by a camera-shake or the like, and an image-blur preventive driving mechanism to drive this optical system.
2. Related Background Art
In an exchangeable lens barrel which is detachably mountable on a single-lens reflex camera, for example, there are incorporated, among others, a zooming mechanism capable of variably adjusting the focal length of a photographic lens system from a telescopic angle to a wide angle, an AF (autofocus mechanism) capable of automatically setting focus on an object to be photographed.
Particularly, in the lens barrels in recent years, an image-blur preventive mechanism is also incorporated for compensating the camera-shake or the like caused by a photographer. There is a conspicuous tendency to make the function of the lens barrel increasingly multiple.
Along with the above-mentioned provision of the multiple function, there are incorporated in a lens barrel of the kind, various driving mechanisms, circuit controllers, and sensors for detecting various pieces of information, among others, together with the optical system using various photographic lenses. Therefore, the implementation of more effective utilization of space in the lens barrel is demanded.
Particularly, according to a lens barrel of the kind, its size is determined to a certain extent by the aperture and others of the optical system of the photographic lens to be incorporated in it. Thus it is not desirable to make its size larger than necessary. Therefore, the dead space in the lens barrel should be efficiently utilized to the utmost in order to arrange an effective assembling of the various driving mechanisms including an electric motor and others, the circuit controller formed by the electric circuits and the like, and also, sensors, among others.
Now, the lens barrel described above is provided with a fixed cylinder as the main body of the barrel, and on the external side thereof, a rotational cylindrical member is rotatively installed to provide various operational rings and the like. At the same time, there are arranged in the fixed cylinder, a supporting cylinder for the optical system of photographic lenses, and a movable cylinder for adjusting the required optical lens system to shift in the direction of the optical axis or in the direction orthogonal to the optical axis, and also, a driving mechanism thereof.
Also, it is necessary to arrange and incorporate the driving circuits for controlling the various driving mechanisms described above, the various sensors for detecting the current status of the camera, and further, wiring means such as a flexible printed board (hereinafter referred to as an FPC) for connecting these elements in appropriate locations in the lens barrel.
However, in a conventional lens barrel, the following problems are encountered when actually installing a circuit assembly formed by the FPC having the driving circuits arranged on it to receive signals from the controllers of the various driving mechanisms, the sensors, and others in a location where the rotary cylinder is rotatively fitted onto the outer circumference of the fixed cylinder.
In other words, since the rotary cylinder is fitted onto the outer circumference of the fixed cylinder, it is impossible to mount the circuit assembly such as the FPC board and others in this portion.
Therefore, it is conventionally practiced that when installing the circuit assembly such as the FPC board, a part of the installation member such as a bent plate affixed to the portion other than the aforesaid fitting portion of the fixed cylinder is extended to the space formed between the outside of the rotary cylinder and the external cover of the lens barrel, and then, the circuit assembly arranged by the FPC board and others is mounted at the extended end thereof to implement the actual assembling.
Therefore, in a conventional structure of the kind, there is a need for using a bent plate and other installation members to mount the circuit assembly arranged by the FPC board and others, hence leading to the problems of the increased number of parts, the complicated workability of assemblies following it, and the eventual increase of the manufacturing cost, among others.
Also, the mounting portion at the extended end of the installation member such as a bent plate is a fixed part, thus necessitating an escape between this fixed part and the rotary cylinder. Therefore, the rotary cylinder, the bent plate, and others are restricted to the extent that such an escape should be arranged. This results in a problem that the area of the available space is reduced for the installation of the circuit assembly formed by the FPC board and others.
Now, in the conventional lens barrel having the image-blur preventive function in it, the image-blur preventive driving mechanism for driving the blur prevention lens, and a blur detection sensor for detecting the blur condition, such as a camera-shake caused by the photographer, are arranged by connecting them to one and the same member, that is, one flexible printed-circuit board (hereinafter referred to as an FPC board), for example. As a result, the problems are inevitably encountered as given below.
In other words, in an image-blur preventive mechanism of the kind, a blur detection sensor is arranged on the X- and Y-axis sides, respectively, in order to detect the blurring condition due to the camera-shake or the like caused by the photographer with respect to the camera, or the lens barrel, in the directions of the orthogonal two axes, that is, the X- and Y-axis directions, on the plane perpendicular to the optical axis of the lens. Therefore, a severe adjustment should be made to position these sensors.
However, in order to position the sensors on the X- and Y-axis sides by adjusting its positions, it is necessary to conduct a fine adjustment for each of the sensors and a rotational adjustment of the fixed cylinder as well. In such a case, if the image-blur preventive driving mechanism and others are mounted integrally on the portion of the fixed cylinder as described earlier, these elements must also be allowed to rotate.
Then, when the image-blur preventive driving mechanism and others are caused to rotate together, these driving mechanism and others may become a source for defectiveness. Also, the rotation of an element having a heavy weight, such as the driving mechanism may cause defective adjustment of the blur detection sensor defective or difficulty in making an appropriate adjustment.
Particularly, in the above-mentioned image-blur preventive driving mechanism, its position must be adjusted rigidly in the same manner as the sensor. It is imparative, therefore, that the relative positioning should be carried out between these two members. Therefore, the adjustment and other related operations are not only complicated, but also create the problem wherein accurate adjustments become difficult to make. In addition a considerable time and labor is required to build in the FPC board in these portions.
Also, in the conventional lens barrel, an AF mechanism and others are arranged with respect to the fixed cylinder which is a fixed member formed in a series in the fixed cylinder unit. Thus an adjustment operation is needed for a portion where an AF mechanism of the kind is installed with some others. Under such circumstances, it is desired that the workability should be improved, and at the same time, the accuracy of the assembling should be secured in a better condition.
Therefore, in a lens barrel of the kind having the aforesaid image-blur preventive function in it, considerations must also be given to the assembling workability in a portion where the AF mechanism is incorporated. Further, a formation of wiring is required to be arranged in this portion, too, by use of an FPC board and others. As a result, considerations should be given equally to the wiring structure and others for the entire body of the lens barrel including the wiring connection with this AF mechanism. Hence it is desired that some measure should be taken to meet all these requirements satisfactorily.
Now, in a lens barrel of the kind having the above-mentioned image-blur preventive function in it, when arranging on the fixed member of the barrel a printed-circuit board having a blur detection sensor assembled thereon, it is conceivable that lead lines can be used to connect the blur detection sensor externally with a circuit controller which controls a blue preventive driving mechanism and others, for example, and that such connection can be made by soldering the lead lines directly on the printed-circuit board where the blur detection sensor is assembled.
However, a connecting method of the kind which uses lead lines requires a plurality of lead lines to be fixed by soldering them on given locations of the assembly board in an extremely limited space. Thus, not only is the operation difficult, but also a considerable time is required to complete this operation.
Particularly, for the blur detection sensor, it is necessary, among others, to adjust its fixing position and posture rigidly with respect to the fixed member. Hence a problem is created as given below when carrying out the positional adjustment of the blur detection sensor and connections by use of the lead lines.
In other words, the position of the blur detection sensor is adjusted once, and then, the above-mentioned plurality of lead lines should be soldered in a state that the assembly board is fixed to the fixed member. Therefore, if the blur detection sensor should be displaced during this soldering work, there is a need for the lead lines to be removed. Then the adjustment should be made again, and only after that, the soldering can be resumed.
Also, considerations must be given so that when the lead lines are arranged and soldered after the execution of the positional adjustment of the blur detection sensor as described above, the lead lines should be prevented from being in contact with the blur detection sensor. This precaution is necessary because if any one of the lead lines abuts upon the blur detection sensor, it can be a cause of presenting detection errors. An occurrence of the kind of event should be avoided under any circumstances.
Here, another problem is encountered wherein it takes a considerable time and labor to execute this work carefully so as to avoid any contact between the lead lines and the blur detection sensor.
Particularly, in the above-mentioned lens barrel, each of the blur detection sensors for the image-blur prevention is arranged on the X- and Y-axis side in order to detect the condition of blur resulting from the camera-shake caused by the photographer with respect to the camera, or the lens barrel. Here, the problem of workability as described above presents itself more conspicuously. Therefore, it is demanded that some measures be taken to solve these problems.